MATLAB: Argument to dynamic structure reference must evaluate to a valid field name.

Question

Argument to dynamic structure reference must
evaluate to a valid field name.
Error in godmake (line 43)
 r=2/pi*(atan(c.(sqrt(((Ixx-Iyy).^2+4*Ixy.^2)/(Ix.^2+Iy.^2)))));

I m getting error in this.how to rectify this error?

my code is:

    clc;
    myFolder = 'G:\pro\aluminium_foil';
    filePattern = fullfile(myFolder, '*.png');
    jpegFiles = dir(filePattern);
    sigma=2;
    for k = 1:length(jpegFiles)
      baseFileName = jpegFiles(k).name;
      fullFileName = fullfile(myFolder, baseFileName);
      %fprintf(1, 'Now reading %s\n', fullFileName);
      I = imread(fullFileName);
    end
    for s=1:length(sigma)
                sigma = sigma(s);
                Wx =  floor(3*sigma);
                x = [-Wx:Wx];
                [xx,yy] = meshgrid(x,x);
                g0 = -exp(-(xx.^2+yy.^2)/(2*sigma^2))/(2*pi*sigma^4);
               F{s}.Gx = xx.*g0;            
                F{s}.Gy = yy.*g0;           
                F{s}.Gxx = (1-xx.^2/sigma^2).*g0;            
                F{s}.Gxy =  -(xx.*yy/sigma^2).*g0;          
                F{s}.Gyy = (1-yy.^2/sigma^2).*g0;
                sij = sigma; 
            Ix = sij*imfilter(I,F{s}.Gx ,'same', 'replicate'); 
            Iy = sij*imfilter(I, F{s}.Gy, 'same', 'replicate');        
            Ixx = sij^2*imfilter(I, F{s}.Gxx, 'same', 'replicate');  
            Ixy = sij^2*imfilter(I, F{s}.Gxy, 'same', 'replicate');  
            Iyy = sij^2*imfilter(I, F{s}.Gyy, 'same', 'replicate');  
     Ix=double(Ix);
     Iy=double(Iy);
     Ixx=double(Ixx);
     Ixy=double(Ixy);
     Iyy=double(Iyy);
        g = sqrt(Ix.*Ix + Iy.*Iy); 
            figure,imshow(g),title('g')
             d =  sqrt( (Ixx-Iyy).^2+ 4*Ixy.^2 );
            figure,imshow(d),title('d')
     SI = 0.5-1/pi*atan((-Ixx-Iyy)./sqrt((Ixx-Iyy).^2+ 4*Ixy.^2));
     figure,imshow(SI),title('SI')
     r=2/pi*(atan(c.(sqrt(((Ixx-Iyy).^2+4*Ixy.^2)/(Ix.^2+Iy.^2)))));
                figure,imshow(r),title('r')
    end

thanks in advance

Answer 1

Replace that line by:

r=2/pi*(atan(c*(sqrt(((Ixx-Iyy).^2+4*Ixy.^2)/(Ix.^2+Iy.^2)))));

There is a typo error...instead of *, . has appeared, so MATLAB expecting c a structure.